3 million Americans are affected by anemia, according to the National Heart, Lung, and Blood Institute. While some of these cases are genetic or caused by other health disorders, the vast majority are the result of an iron deficiency. Iron-deficiency anemia can occur when your body doesn't have enough iron to produce hemoglobin.

“Hemoglobin is a protein attached to red blood cells that carries oxygen from the lungs to the rest of the body; iron is a critical component of hemoglobin. Iron is absorbed in the small intestine, where it then travels through the blood to bone marrow, where it is involved in red blood cell formation,” explains nutritionist Rania Batayneh, M.P.H., the owner of Essential Nutrition for You and the author of The One One One Diet.

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When there’s not enough iron, due to eating less of the mineral, reduced absorption, increased requirements (say, during pregnancy or growth spurts), or blood loss (including menstruation and wounds), your body is less efficient at delivering oxygen to your muscles, heart, brain and other tissues. Subsequently, here are nine subtle symptoms you might have iron-deficiency anemia, according to Batayneh and Erin Thole-Summers, R.D, a registered dietitian and sports nutrition consultant in West Des Moines, Iowa.

You’re tired, like all the time.

It’s tough to catch your breath.

Your head is achy or you feel lightheaded.

A quicker than normal heartbeat, on occasion.

Your hands and feet are constantly cold.

Mild chest pain.

Skin appears pale and nails are brittle or break.

Your hair is falling out at a more rapid pace.

Dizziness.

“If you notice any of these symptoms that might point to an iron deficiency, seek help from a doctor or registered dietitian for a quick blood test. A professional can help you identify the cause of iron-deficiency anemia, which is important as it may be an underlying side effect of other diseases or issues, including ulcers, hernias, parasites, or certain cancers,” Batayneh says.

In the meantime—and after said blood test—you can start making a dent in your iron deficiency, zero pills or potions required. Your Rx: Eat more of the mineral.

“It can take one to two months to restore normal iron levels, depending upon how severe the deficiency is,” Thole-Summers says.

Interestingly, your body is able to absorb and put to use 14 to 18 percent of iron you consume if you mix up meats, seafoods, and plant-based sources, and about 5 to 12 percent of iron consumed via vegetarian items alone. Research has found that you can err closer to that 12 percent, even while completely vegan, if you pair your iron sources with vitamin C.

“C can be found in many vegetables, like bell peppers and broccoli, as well as citrus fruits, and helps increase help their absorption,” Batayneh says. “Fortified and plant-based foods contain a less-absorbable version of iron called non-heme iron, so you may need to up your intake of these foods to regain normal iron levels in the blood.”

Aim for a total of 18 milligrams per day to hit the mark recommended by the National Institutes of Health (NIH). Thole-Summers recommends these six food sources as top options:

Legumes

Caitlin Bensel

Beans, lentils, chickpeas, peas, and soybeans are a great source of iron, especially for vegetarians. One cup of cooked lentils contains 6.6 milligrams, which is about one-third of the iron you need in a day.

Tofu

Caitlin Bensel

Beyond the 20 grams of protein per half-cup serving, this soy product packs in 3.6 milligrams of iron (19 percent of the RDI). “Tofu is also a good source of thiamine and several minerals, including calcium, magnesium and selenium,” Thole-Summers says.

Red meat

Photo: Jennifer Causey

“A 3 ½-ounce serving of ground beef has 2.7 milligrams of iron, which is 15 percent of the recommended daily intake (RDI),” Thole-Summers says. Meat is also rich in protein, zinc, selenium and several B vitamins. Researchers have suggested that iron deficiency may be less likely in people who eat meat, poultry and fish on a regular basis. Note, red meat does not need to be consumed on a daily basis but rather a couple times a week to prevent high cholesterol levels.

Quinoa

Ann Taylor Pittman

“Gluten-free quinoa is higher in protein than many other grains, as well as rich in folate, magnesium, copper, manganese and many other nutrients,” Thole-Summers says. One cup of cooked quinoa provides 2.8 milligrams of iron, about 15 percent of the RDI and slightly more than that just-mentioned burger meat.

Spinach

Caitlin Bensel

In addition to being low in calories, spinach is rich in both non-heme iron and vitamin C—making it a superstar in terms of plant-based iron absorption. A 3-½ ounce serving of cooked spinach contains 3.6 milligrams of iron, or approximately 20 percent of the RDI.

Shellfish

Victor Protasio

“All shellfish is high in iron, but clams, oysters and mussels are particularly good sources. For instance, a 3 ½-ounce serving of clams may contain up to 28 milligrams of iron, which is 155 percent of what you need in a day,” Thole-Summers says. She cautions, however, that the iron content of clams is highly variable, and some types may contain much lower amounts. Still, “the iron in shellfish is heme iron, which your body absorbs more easily than the non-heme iron found in plants. A serving of clams also provides 26 grams of protein, 37 percent of the RDI for vitamin C and a whopping 1,648 percent of the RDI for vitamin B12. In fact, all shellfish is high in nutrients and has been shown to increase the level of heart-healthy HDL cholesterol in your blood,” she says.